Progeny testing
Progeny
testing enables the assessment of the breeding qualities of separate spawners
or pairs of spawners and the selection of the best for further selection work.
However, progeny testing will increase the generation interval very markedly.
For example, in carp breeding it requires one or two years, which would mean a
slowing down of selection work by 20 to 30 per cent.
Three
methods of progeny testing are applicable in aquaculture. The first method is
testing of pairs, without testing males and females separately (fig. 8.4a). The
second is to test spawners belonging to one sex, as for example females only as
shown in fig. 8.4b, and the third is the testing of both females and males
(complete diallele crossing) (fig. 8.4c).
The
equation to measure selection response is the same as in family selection.
Intensity of selection is limited by the number of families. Variability of
family means (sf) is also the same in both cases. Heritability of
family means (h2f) in progeny testing is high, as in
family testing. This may occur only if the breeding conditions of all progenies
are practically identical or if breeding proceeds with a three- or four-fold
reiteration.
By
comparing the response values in the two equations (R = Sh2 and Rf
= Sfh2f), it should be possible to determine
which method is more efficient in a given programme. If Sh2 is
greater than Sfh2, mass selection is more effective than
selection for relatives. The selection for relatives is only advantageous when
the increase in heritability is not accompanied by a proportionally greater
drop in the selection differential.
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